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Old   August 4, 2013, 04:03
Default Additional Variable
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Ding Chao
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Hi everyone.
I am modeling a gas-water free surface flow useing CFX-14. I have created a additional variable and the source exist in the water phase. The additional variable should only exist in the water phase,but finally I found it spread into the air phase, and this is not what I want.
How can I solve this problem?If anyone know the answer,please help me.I will be very grateful to you
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Old   August 4, 2013, 06:00
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Glenn Horrocks
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What type of additional variable is it (what equation did you select to model it)?

Physically, why doesn't it spread to the air phase?

Wouldn't a diffusivity (assuming it is a diffusive AV, I am just guessing here) which has a value in the liquid but is zero (or close to it, like 1e-20) in air do the trick?
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Old   August 4, 2013, 06:36
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Quote:
Originally Posted by ghorrocks View Post
What type of additional variable is it (what equation did you select to model it)?

Physically, why doesn't it spread to the air phase?

Wouldn't a diffusivity (assuming it is a diffusive AV, I am just guessing here) which has a value in the liquid but is zero (or close to it, like 1e-20) in air do the trick?
The type of additional variable is specific scalar and when the air.vf>0.5,the source will be 0. The transport type in water phase is Transport Equation,and in air phase,the transport equation is off.
The additional variable can be seen as a kind of chemical substances,and it can only exist in liquid phase.
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Old   August 4, 2013, 07:24
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Glenn Horrocks
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How is it spreading into the air? Can you post an image? Or show a conservation balance?
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